The scientists deleted the faulty genes using CRISPR CAS - the most versatile tool in bio-technology which can add and remove parts of a DNA sequence with pin-point accuracy.

New Delhi: A group of scientists in the US have taken the first steps in tweaking the genes in the human embryo - a subject fraught with fears of an eventual designer baby and a minefield of ethical dilemma. The scientists say their research has the potential to eliminate diseases that run through some families.

The list of such diseases is long - it includes diabetes, hypertension, haemophilia, thalassemia, Down's syndrome and even certain cancers.

For now, the scientists had removed a mutated gene from a human embryo, which, they said can cause heart attack.

The scientists deleted the faulty genes using CRISPR CAS - the most versatile tool in bio-technology which can add and remove parts of a DNA sequence with pin-point accuracy. The healthy embryos were then allowed to grow further - but only for a few days.

An account of the research, complete with photos of the multiplying cells, was published in the prestigious British journal "Nature". For obvious ethical considerations, the embryo was not implanted in any woman.

The scientists say had the embryo been allowed to mature, the successive generations would have been free from the faulty gene. "By using this technique, it's possible to reduce the burden of this heritable disease on the family and eventually the human population," said Shoukhrat Mitalipov, the chief of Center for Embryonic Cell and Gene Therapy at Oregon Health and Science University.

The scientists are well aware of the ethical issues their latest research has thrown up. The possibility of scientifically modifying humans - the object of some of the most twisted research by the Nazis - had re-surfaced after the huge strides in gene research and reproductive technology made over the last few decades.

"Gene editing is still in its infancy... it is crucial that we continue to proceed with the utmost caution, paying the highest attention to ethical considerations," said Juan Carlos Izpisua Belmonte, a professor in Salk Institutes Gene Expression Laboratory and a co-author of the paper.